Expected Loss to be Paid - Narrative (Details)	12 Months Ended						12 Months Ended		0 Months Ended										0 Months Ended									12 Months Ended											12 Months Ended		12 Months Ended									12 Months Ended																12 Months Ended								12 Months Ended																12 Months Ended								12 Months Ended																12 Months Ended				12 Months Ended						12 Months Ended			12 Months Ended								12 Months Ended					12 Months Ended									0 Months Ended					12 Months Ended															12 Months Ended										12 Months Ended
	Dec. 31, 2013 USD ($) Payment		Dec. 31, 2012 USD ($)		Dec. 31, 2011	Dec. 31, 2013 Puerto Rico USD ($)	Dec. 31, 2013 Refinancing Risk on Three Largest Infrastructure Transactions AUD	Dec. 31, 2013 Refinancing Risk on Three Largest Infrastructure Transactions USD ($)	Jun. 21, 2013 Flagstar USD ($)	Dec. 31, 2013 BIG USD ($)		Dec. 31, 2012 BIG USD ($)		Dec. 31, 2013 BIG Puerto Rico USD ($)	Dec. 31, 2013 Bank of America Agreement USD ($)	Apr. 14, 2011 Bank of America Agreement USD ($)	Dec. 31, 2013 Deutsche Bank Agreement USD ($)		Oct. 10, 2013 Deutsche Bank Agreement External Credit Rating, Non Investment Grade USD ($)	Dec. 31, 2013 UBS and Third Party Agreement USD ($)		May 06, 2013 UBS and Third Party Agreement	Oct. 10, 2013 Covered Transactions Deutsche Bank Agreement USD ($)	May 08, 2012 Covered Transactions Deutsche Bank Agreement USD ($) Transaction	Dec. 31, 2013 Uninsured Tranches of Covered Transactions Deutsche Bank Agreement USD ($)	Oct. 10, 2013 Uninsured Tranches of Covered Transactions Deutsche Bank Agreement USD ($)	May 08, 2012 Uninsured Tranches of Covered Transactions Deutsche Bank Agreement USD ($)	Dec. 31, 2013 Minimum Refinancing Risk on Three Largest Infrastructure Transactions	Dec. 31, 2013 Maximum Refinancing Risk on Three Largest Infrastructure Transactions	Dec. 31, 2013 U.S. dollar denominated obligations Minimum	Dec. 31, 2012 U.S. dollar denominated obligations Minimum	Dec. 31, 2013 U.S. dollar denominated obligations Maximum	Dec. 31, 2012 U.S. dollar denominated obligations Maximum	Dec. 31, 2013 Total first lien scenario	Dec. 31, 2012 Total first lien	Dec. 31, 2011 Total first lien	Dec. 31, 2013 Total first lien Bank of America Agreement USD ($)		Dec. 31, 2013 Total first lien Base Scenario	Dec. 31, 2013 Total first lien Somewhat More Stressful Environment	Dec. 31, 2013 Total first lien Somewhat Less Stressful Environment	Dec. 31, 2013 Alt-A first lien USD ($)		Dec. 31, 2012 Alt-A first lien USD ($)		Dec. 31, 2011 Alt-A first lien		Dec. 31, 2013 Alt-A first lien BIG USD ($)	Dec. 31, 2012 Alt-A first lien BIG USD ($)	Dec. 31, 2013 Alt-A first lien Somewhat More Stressful Environment USD ($)	Dec. 31, 2013 Alt-A first lien More Stressful Environment USD ($)	Dec. 31, 2013 Alt-A first lien Somewhat Less Stressful Environment USD ($)	Dec. 31, 2013 Alt-A first lien Less Stressful Environment USD ($)	Dec. 31, 2013 Alt-A first lien Minimum		Dec. 31, 2012 Alt-A first lien Minimum		Dec. 31, 2011 Alt-A first lien Minimum		Dec. 31, 2013 Alt-A first lien Maximum		Dec. 31, 2012 Alt-A first lien Maximum		Dec. 31, 2011 Alt-A first lien Maximum		Dec. 31, 2013 Option ARM USD ($)		Dec. 31, 2012 Option ARM USD ($)		Dec. 31, 2011 Option ARM		Dec. 31, 2013 Option ARM BIG USD ($)	Dec. 31, 2012 Option ARM BIG USD ($)	Dec. 31, 2013 Option ARM Somewhat More Stressful Environment USD ($)	Dec. 31, 2013 Option ARM More Stressful Environment USD ($)	Dec. 31, 2013 Option ARM Somewhat Less Stressful Environment USD ($)	Dec. 31, 2013 Option ARM Less Stressful Environment USD ($)	Dec. 31, 2013 Option ARM Minimum		Dec. 31, 2012 Option ARM Minimum		Dec. 31, 2011 Option ARM Minimum		Dec. 31, 2013 Option ARM Maximum		Dec. 31, 2012 Option ARM Maximum		Dec. 31, 2011 Option ARM Maximum		Dec. 31, 2013 Subprime USD ($)		Dec. 31, 2012 Subprime USD ($)		Dec. 31, 2011 Subprime		Dec. 31, 2013 Subprime BIG USD ($)	Dec. 31, 2012 Subprime BIG USD ($)	Dec. 31, 2013 Subprime Somewhat More Stressful Environment USD ($)	Dec. 31, 2013 Subprime More Stressful Environment USD ($)	Dec. 31, 2013 Subprime Somewhat Less Stressful Environment USD ($)	Dec. 31, 2013 Subprime Less Stressful Environment USD ($)	Dec. 31, 2013 Subprime Minimum		Dec. 31, 2012 Subprime Minimum		Dec. 31, 2011 Subprime Minimum		Dec. 31, 2013 Subprime Maximum		Dec. 31, 2012 Subprime Maximum		Dec. 31, 2011 Subprime Maximum		Dec. 31, 2013 Prime first lien USD ($) scenario	Dec. 31, 2012 Prime first lien USD ($)	Dec. 31, 2013 Prime first lien BIG USD ($)	Dec. 31, 2012 Prime first lien BIG USD ($)	Dec. 31, 2013 Prime first lien Somewhat More Stressful Environment USD ($)	Dec. 31, 2013 Prime first lien More Stressful Environment USD ($)	Dec. 31, 2013 Prime first lien Somewhat Less Stressful Environment USD ($)	Dec. 31, 2013 Prime first lien Less Stressful Environment USD ($)	Dec. 31, 2012 Prime first lien Less Stressful Environment	Dec. 31, 2013 RMBS	Dec. 31, 2013 Second lien Curve	Dec. 31, 2013 Second lien Bank of America Agreement USD ($)		Dec. 31, 2013 Second lien Base Scenario	Dec. 31, 2013 Second lien Scenario 1	Dec. 31, 2013 Second lien Scenario 2	Dec. 31, 2013 Second lien Minimum	Dec. 31, 2013 Second lien Maximum	Dec. 31, 2013 Life Insurance USD ($)	Dec. 31, 2013 Life Insurance BIG USD ($)	Dec. 31, 2013 Life Insurance BIG Ballantyne Re Plc and Orkney Re II Plc Transaction	Dec. 31, 2013 Student Loan USD ($)	Dec. 31, 2013 Asset-backed Student Loan USD ($)	Dec. 31, 2013 Asset-backed Student Loan BIG USD ($)	Dec. 31, 2013 Public Finance - Student Loan USD ($)	Dec. 31, 2013 Public Finance - Student Loan BIG USD ($)	Dec. 31, 2013 TruPS CDOs USD ($)	Dec. 31, 2013 TruPS CDOs BIG USD ($)	Dec. 31, 2013 Puerto Rico BIG USD ($)	Dec. 31, 2013 Public Finance - City of Detroit USD ($)	Dec. 31, 2013 Public Finance - City of Detroit Sewer USD ($)	Dec. 31, 2013 Public Finance - City of Detroit Water Sector USD ($)	Dec. 31, 2013 Public Finance - City of Detroit State General Obligation USD ($)	Dec. 31, 2013 Public Finance - City of Detroit City Certificates of Participation USD ($)	Dec. 31, 2013 Public Finance - Stockton General Fund USD ($)	Dec. 03, 2013 Public Finance - Jefferson County, Alabama Sewer Authority USD ($)	Dec. 31, 2013 Public Finance - Jefferson County, Alabama Sewer Authority USD ($)	Dec. 31, 2013 Public Finance - Harrisburg, Pennsylvania USD ($)	Dec. 31, 2013 Public Finance - Louisville Arena Authority USD ($)	Dec. 31, 2013 Public Finance bonds secured by excess free cash flows of Foxwoods Casino USD ($)	Dec. 31, 2013 Troubled Municipal Credits USD ($)	Dec. 31, 2012 Troubled Municipal Credits USD ($)	Dec. 31, 2013 Spanish sub-sovereign debt EUR (€)	Dec. 31, 2013 Portugal sub-sovereign debt EUR (€)	Dec. 31, 2013 Manufactured Housing Loans USD ($)	Dec. 31, 2012 Manufactured Housing Loans USD ($)	Dec. 31, 2013 Manufactured Housing Loans BIG USD ($)	Dec. 31, 2013 HELOCs USD ($)		Dec. 31, 2012 HELOCs USD ($)		Dec. 31, 2011 HELOCs		Dec. 31, 2013 HELOCs BIG USD ($)	Dec. 31, 2012 HELOCs BIG USD ($)	Dec. 31, 2013 HELOCs Scenario 1 USD ($)	Dec. 31, 2013 HELOCs Scenario 2 USD ($)	Dec. 31, 2013 Closed-end second lien USD ($)		Dec. 31, 2012 Closed-end second lien USD ($)		Dec. 31, 2011 Closed-end second lien		Dec. 31, 2013 Closed-end second lien BIG USD ($)	Dec. 31, 2012 Closed-end second lien BIG USD ($)	Dec. 31, 2013 Closed-end second lien Scenario 1 USD ($)	Dec. 31, 2013 Closed-end second lien Scenario 2 USD ($)	Dec. 31, 2013 Hungarian-infrastructure bonds USD ($)	Dec. 31, 2013 Spanish, Portuguese and Hungarian Debt USD ($)	Dec. 31, 2012 Spanish, Portuguese and Hungarian Debt USD ($)	Dec. 31, 2013 Structured Finance USD ($)	Dec. 31, 2012 Structured Finance USD ($)
Guarantor Obligations [Line Items]
Gross R&W amounts recovered	$ 986,000,000		$ 485,000,000
Period after the end of the reporting period within which the ceded paid losses are typically settled (in days)	45 days
Discount factor (as a percent)																														0.00%	0.00%	4.44%	3.28%
Maximum number of payments behind to be considered performing borrower	1
Period company reduced base scenario	2 months
Period company reduced most optimistic case for market recovery	3 months
Period company extended most pessimistic case for market recovery	3 months
Default estimate liquidation period																																		3 years	2 years	2 years
Increase of expected losses from estimated impact of refinements in assumptions	8,000,000
Period for constant conditional default rate (in months)																																		36 months	24 months
Period for which estimated defaults are attributed to loans currently delinquent or in foreclosure																																		36 months
Period from plateau to intermediate conditional default rate (in months)			36 months		36 months																																		12 months			48 months		36 months		36 months																				48 months																								48 months
Intermediate conditional default rate as a percentage of plateau conditional default rate																																							20.00%
Period of constant intermediate conditional default rate (in months)																																							36 months
Final conditional default rate as a percentage of plateau conditional default rate																																							5.00%
Estimated loss severity rate, one through six months (as a percent)																																		90.00%
Period until which loss severity rate would continue (in months)	18 months		12 months																																																																																							9 months		6 months
Estimated loss severity rate, six through twelve months (as a percent)																																																																																										80.00%
Loss severity (as a percent)																																							40.00%
Period from initial to final conditional prepayment rate (in months)	2 years 6 months		2 years																															12 months							18 months
Current conditional prepayment rate used in alternate scenario for loss estimate (as a percent)																																		15.00%
Conditional Default Rate, Change from Initial Assumption	12 months																																																																																																																											2 months
Intermediate conditional default rate (as a percent)																																																						0.60%	[1]	0.80%	[1]	0.60%	[1]	3.70%	[1]	4.60%	[1]	8.30%	[1]													1.00%	[1]	1.40%	[1]	1.90%	[1]	3.40%	[1]	5.20%	[1]	6.30%	[1]													1.10%	[1]	1.50%	[1]	1.70%	[1]	3.20%	[1]	5.20%	[1]	6.00%	[1]										5.00%
Number of scenarios weighted in estimating expected losses																																																																																																																		5
Increase in the plateau period used to calculate potential change in loss estimate (in months)																																																																																																																						6 months
Increased plateau period used to calculate potential change in loss estimate (in months)																																																																																																																						42 months										4 months
Prior loss severity recovery period used to calculate potential change in loss estimate (in years)																																																																																																																						4 years 6 months
Current loss severity recovery period used to calculate potential change in loss estimate (in years)																																									2 years 6 months																																																																													2 years 6 months
Increased final loss severity for subprime transactions used to calculate potential change in loss estimate (as a percent)																																								60.00%
Increase in expected loss in case of increase in conditional default rate plateau period and loss severity recovery period																																																		41,000,000																								12,000,000																								93,000,000																				4,000,000
Loss severity recovery period used to calculate potential change in loss estimate in even more stressful scenario (in years)																																		9 years
Decreased ramp down period used to calculate potential change in loss estimate (in months)																																																																																																																							15 months		9 months	12 months		28 months			28 months	33 months
Increase in expected loss in case of increase in loss severity recovery period in an even more stressful scenario																																																			111,000,000																								30,000,000																								136,000,000																				12,000,000
Number of scenarios where the recovery was faster than in base case																																		2
Initial subprime loss severity rate assumed for 12 months (as a percent)																																									80.00%
Initial subprime loss severity rate assumed to be recovered over two years (as a percent)																																									40.00%
Increase (decrease) in expected loss in case of less gradual conditional default rate recovery and changes in initial subprime loss severity rate																																																				1,000,000																								(11,000,000)																								(24,000,000)																				(1,000,000)
Decrease in the plateau period used to calculate potential change in loss estimate (in months)																																		6 months
Decreased plateau period used to calculate potential change in loss estimate (in months)																																		30 months
Decrease in expected loss in case of decrease in conditional default rate plateau period																																																					38,000,000																								29,000,000																								77,000,000																				4,000,000
Typical past due period for loans to be charged off (in days)																																																																																																																												180 days
First delinquency category (in days)																																																																																																																																		30 days	59 days
Second delinquency category (in days)																																																																																																																																		60 days	89 days
Third delinquency category (in days)																																																																																																																																		90 days	119 days
Fourth delinquency category (in days)																																																																																																																																		120 days	149 days
Fifth delinquency category (in days)																																																																																																																																		150 days	179 days
Period of loan default estimate																																																																																																																												5 months
Number of preceding months average liquidation rates used to estimate loan default rate																																																																																																																												12 months
Number of months CDR is calculated by applying liquidation rates to past due balances																																																																																																																												4 months
Stress period (in months)																																																																																																																												34 months			34 months	42 months	24 months
Number of months of delinquent data																																																																																																																												5 months
Period of constant conditional default rate (in months)																																																																																																																												1 month			1 month		1 month
Loss recovery assumption (as a percent)																																																																																																																												2.00%
Conditional prepayment rate base case, average number of quarters																																																																																																																												3 months
Final conditional prepayment rate (as a percent)																																										15.00%	[1]	15.00%	[1]	15.00%	[1]																			15.00%	[1]	15.00%	[1]	15.00%	[1]																			15.00%	[1]	15.00%	[1]	15.00%	[1]																													10.00%																																					10.00%	[1]	10.00%	[1]	10.00%	[1]					10.00%	[1]	10.00%	[1]	10.00%	[1]
Number of conditional default rate curves modeled in estimating losses																																																																																																																												3
Increase in conditional default rate ramp down period	5 months
Change in estimate for increased conditional default rate plateau period																																																																																																																																																																									26,000,000
Decreased conditional default rate ramp down period																																																																																																																																	18 months
Change in estimate for decreased conditional default rate ramp down period																																																																																																																																																																										24,000,000									2,000,000	2,000,000
Amount of liabilities agreed to be paid by entities providing R&W for transaction in which the Company provided insurance	3,611,000,000
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	712,000,000
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates, agreements with R&W providers	413,000,000
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates in pursuit	299,000,000
Loss sharing percentage																80.00%						85.00%
Proceeds from Legal Settlements									105,000,000
Maximum loss up to which loss sharing percentage applicable																6,600,000,000
Collateral losses															3,700,000,000
Estimated cumulative collateral losses															5,100,000,000
Loss sharing percentage, first layer																								80.00%			60.00%
Maximum aggregate collateral losses up to which first layer of loss sharing will be applicable																								319,000,000			141,000,000
Minimum losses at which second later of loss sharing percentage becomes applicable																								389,000,000			161,000,000
Loss sharing percentage, second layer																								85.00%
Maximum aggregate collateral losses up to which second layer of loss sharing will be applicable																								600,000,000
Number of transactions insured																								8																																																																																																														2
Minimum losses at which third layer of loss sharing percentage becomes applicable																											185,000,000
Loss sharing percentage, third layer																											100.00%
Maximum aggregate collateral losses up to which third layer of loss sharing will be applicable																											248,000,000
Insured financial obligations, gross outstanding principal amount	487,895,000,000		550,907,000,000																						150,000,000																																																																																																																																																															78,005,000,000	99,723,000,000
Estimated reimbursement amount, collateral losses																										30,000,000
Insured financial obligations, net outstanding principal amount																							294,000,000
Amount of assets agreed to release in excess of amount of assets required to be held in trust																			60,000,000
Financial guaranty insurance contracts, principal amount not covered under agreements	1,617,000,000
Financial guaranty insurance contracts, principal amount already covered under agreements but company projects receiving additional amounts	806,000,000
Financial guaranty insurance contracts, principal amount	5,958,000,000	[2]						3,000,000,000									1,711,000,000	[2]		807,000,000	[2]																1,059,000,000	[2]																																																																																							1,387,000,000	[2]							2,700,000,000		2,800,000,000	1,900,000,000	206,000,000	900,000,000	253,000,000	5,000,000,000	1,700,000,000			1,000,000,000	784,000,000	146,000,000	175,000,000			600,000,000	189,000,000							257,000,000		180,000,000
Loss and loss adjustment expense reserve	592,000,000		601,000,000																																																																																																																																		598,000,000																				116,000,000
Net exposure of debt																																																																																																																																															2,100,000,000					119,000,000				336,000,000				313,000,000	80,000,000																								608,000,000
Projected net expected loss																																																																																																																																					73,000,000		64,000,000					51,000,000														264,000,000	7,000,000
Increase (decrease) in projected expected loss to be paid							413,000,000																																																																																																																													66,000,000			10,000,000					24,000,000														257,000,000
Reimbursements Received for Claims Previously Paid																																																																																																																																												9,000,000
Net Par Outstanding (excluding loss mitigation bonds)	459,107,000,000	[3]	518,772,000,000	[3]		5,400,000,000				22,538,000,000	[3]	22,297,000,000	[3]	5,171,000,000																												3,590,000,000		4,469,000,000				2,728,000,000	3,454,000,000																	937,000,000		1,450,000,000				598,000,000	1,042,000,000																	6,130,000,000		7,048,000,000				1,945,000,000	2,061,000,000																	541,000,000	641,000,000	403,000,000	475,000,000																									5,200,000,000																			2,279,000,000		3,079,000,000				1,897,000,000	2,576,000,000			244,000,000		348,000,000				146,000,000	231,000,000						72,928,000,000	93,303,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss																																																																																																																																							26,000,000																							26,000,000	33,000,000
Percent of net par outstanding financial guaranty insurance in credit default swap form																																																																																																																																												72.00%
Net claims paid																																																																																																																																																				26,000,000
Senior Warrants Issued by Third Party																																																																																																																																																					1,785,000,000
Net claims paid to date																																																																																																																																																									145,000,000
Gross exposure of debt																																																																																																																																																												437,000,000	92,000,000																								645,000,000
Expected LAE for mitigating claim liabilities	34,000,000		39,000,000																																																																																																																																																																																			51,000,000	41,000,000
Estimated years for recoveries of infrastructure transactions																												10 years	35 years
Financial insurance guaranty, infrastructure finance, possible claims requiring payment, gross before reinsurance								1,800,000,000
Paid LAE	$ 54,000,000		$ 47,000,000

[1] Represents variables for most heavily weighted scenario (the “base case”).

[2] This table relates to past and projected future recoveries under R&W and related agreements. Excluded is the $299 million of future net recoveries the Company projects receiving from R&W counterparties in transactions with $1,617 million of net par outstanding as of December 31, 2013 not covered by current agreements and $806 million of net par partially covered by agreements but for which the Company projects receiving additional amounts.

[3] In the third quarter of 2013, the Company adjusted its approach to assigning internal ratings. See "Refinement of Approach to Internal Credit Ratings and Surveillance Categories" above. This approach is reflected in the "Financial Guaranty Portfolio by Internal Rating" tables as of both December 31, 2013 and December 31, 2012.